Spectrum sharing is thought of as one of the most viable ways of improving the amount of spectrum available to wireless networks and other radio devices for conducting wireless communications. An exemplary spectrum sharing technique involves use of television white spaces under regulations set forth by an appropriate regulatory agency. An exemplary regulatory agency that regulates the use of wireless spectrum is the U.S. Federal Communications Commission (FCC). Other countries may have similar regulatory entities.
In the U.S., for example, the FCC has eliminated analog television (TV) broadcasts in favor of digital TV broadcasts. This has freed spectrum channels for use by unlicensed radio systems to offer various services, such as mobile communications and Internet access. In this context, the freed spectrum is commonly referred to as TV white space (or TVWS) but other types of white spaces are possible. In the case of TV white space, the white space is comprised of unused spectrum that is interleaved with spectrum used by incumbent radio devices in the channel 2 to channel 51 range (corresponding to 54 MHz to 698 MHz). Exemplary incumbent radio devices for TV white space include television broadcasters and other priority users of television channels. Under FCC regulations, for example, radio devices that use TVWS must register with a central database server (also referred to as a spectrum management server) and receive a channel list (also referred to as a channel map) of available channels for which the radio device may use in a shared environment with other TV band devices (TVBDs) while minimizing the possibility of creating undesirable interference to incumbent radio systems. The channel list that is generated for a radio device is generated by the central database server based on the location of the radio device. In this manner, the operation of incumbent radio devices having protected areas in which the radio device is located may be taken into account when determining channel availability.
Also, regulators and industry groups have proposed the use of geo-location database technology to control or manage spectrum access for radios in other situations. For example, use of geo-location database technology has been proposed for the 5 GHz UNII bands and for the 3.550 GHz to 3.650 GHz bands in which the U.S. government and military are incumbent users.
Outside the U.S., use of geo-location database technology has been proposed for TVWS bands in a number of countries. In the European Union (EU), TVWS sharing is often referred to as authorized shared access (ASA) and/or licensed shared access (LSA). Exemplary regulations for ASA/LSA are outlined in European Telecommunications Standards Institute (ETSI) EN 301 598. Other standards bodies have also proposed mechanisms for supporting spectrum sharing, such as the Internet Engineering Task Force's (IETF) Protocol to Access White Space (PAWS).
In white space networks, users of white space channels communicate with a database server (also referred to as a white space database (WSDB), geo-location database, spectrum management server, or white space allocation management system) to acquire specific spectrum access credentials that are a function of the location of the user. An exemplary set of specific spectrum access credentials is a white space channel list (also referred to as a channel map) that authorizes the user device to transmit on specified channels, at a specified location, at a maximum power, and for a specified period of time. One type of white space user is a master white space device (WSD) (sometimes referred to as a hub). Communications between the master WSD and the database server are over a medium that does not cause impermissible interference to a protected radio device. Typically, the medium involves the Internet to which the master WSD connects via a terrestrial connection or a cellular connection. As a result, master devices typically have Internet access to a TVWS database server over a medium that does not rely on TV white spaces and may make channel lists requests directly with the TVWS database server. An exemplary master WSD in this situation may be a fixed-location TVDB device.
Another type of white space user is a slave WSD (sometimes referred to as a spoke). A slave WSD does not have independent access to the Internet. To acquire a channel list from the database server, the slave WSD uses a radio link established with the master WSD over a white space channel as a pathway for Internet access. As such, the master WSD serves as an intermediary for communications between the slave WSDs and the database server. In this arrangement, the master WSD may proxy control data communications between the slave WSDs and the TVWS database server. As a result, slave devices may not have Internet access to a TVWS database server over a medium that does not rely on TV white spaces. Thus, slave devices typically depend on master WSDs to forward channel list request and other control messages to or from the TVWS database server. An exemplary slave WSD in this situation may be a mobile TVDB device, but it is possible that the slave WSD could be a fixed-location TVBD device.
Under certain white space regulations, master and slave devices periodically make requests and to a TVWS database server to update their respective lists of available white space channels and associated power limits. In some circumstances, slave WSDs make these requests every fifteen minutes. As the number of dependent slave devices grows, so does the amount of control data traffic generated between master and slave devices on the white space channels used to support the respective interfaces. The control data exchanged between devices reduces the wireless capacity available for exchanging user data on the affected white space channels.
A typical message flow for data exchange between a slave WSD 10 and a TVWS database server 12 under the conventional approach is shown in FIG. 1. In this data exchange, a master WSD 14 serves as an intermediary. At step 16, the master WSD 14 may broadcast a beacon containing generic parameters under which the slave WSD 10 may use to communicate with the master WSD 14 before the slave WSD 10 acquires specific spectrum access credentials. The WSD 14, after receipt of the beacon, sends a channel list request to the master WSD 14 at step 18. Upon receipt of the channel list request, the master WSD 14 sends a channel list request on behalf of the slave WSD 10 to the TVWS database server 12 at step 20. The TVWS database server 12 processes the channel list request and responds to the master WSD 14 at step 22 with specific spectrum access credentials for the slave WSD 10 (e.g., a channel list response). At step 24, the master WSD 14 sends the specific spectrum access credentials (e.g., the channel list response) from step 22 to the slave WSD 10.
Following receipt of the specific spectrum access credentials by the slave WSD 10, the slave WSD 10 selects a channel in the specific spectrum access credentials to use for wireless communications. The channel use selection is communicated to the master WSD 14 as a channel use notification at step 26 and the master WSD 14 communicates the channel use notification to the TVWS database server 12 at step 28. An acknowledgement in the form of a channel use response is sent from the TVWS database server 12 to the master WSD 14 at step 30 and the master WSD 14 communicates the channel use response to the slave WSD 10 at step 32.